Judith Collins is determined to remain National's leader even if the party fails to grab power at the election.

"Yes, I will be staying on," she told reporters today after being asked about her post-election plan if National was not successful.

Collins spent this morning on a walkabout in the upmarket Auckland suburb of Ponsonby with Auckland Central candidate Emma Mellow.

The National leader returned to the Super City from Christchurch this morning after The Press' leaders debate last night where Collins and Ardern had memorable exchanges over the price of milk, respect for Samoa and pokes at each others' fiscal plans.

There was a particularly intense exchange over climate change and farming, where Collins praised the agriculture sector's importance to the export economy.

"Understand this: there is no free lunch for us in this world. We are a little country that has to fight for every trade deal," Collins said.

"We need to wake up ... we have to pay for health, we have to pay for education."

Ardern retorted that farmers were already playing their part in the climate change conversation, making New Zealand a world-leader despite the country's relatively tiny contribution to global emissions.

"Unless we move on this, we will be left behind and we will lose our brand. Dairying is doing well ... as we work on these environment issues together.

"It is a sad day when we give up on our reputation of being clean and green," said Ardern.

It was the pair's third debate and the first time Ardern was widely declared the winner.

Collins told The AM Show this morning she thought she "did well in the debate" and said Ardern had more energy than she'd had in their previous debates.

"This time she realised she's supposed to be in the competition. I thought it was a great debate and I felt very good at the end of it. In fact, I felt quite energised at the end of it all.

"I thought I did well and I thought she did a better job than she's done before."

Collins has this week come under fire after MP for Maungakiekie Denise Lee sent an email, which was then leaked, to her caucus colleagues questioning why she was kept in the dark about a policy to review Auckland Council.

Collins this morning said she'd "dealt with it" and said Lee's actions were a "bit of funny behaviour".

"It's just important that you know, in the campaigns, certainly with the campaigns I've been involved in, the leader and the leadership team, the campaign team as well, have to make decisions.

"Those decisions are made and [they don't] always include people who particularly have been involved in the areas, particularly if it's not the decision that person might have wanted. We just get on and do the job."